Variable-output hydraulic pump



July 24, 1951 L, EECH 2,561,519

VARIABLE-OUTPUT HYDRAULIC PUMP Filed Feb. 19. 1948 5 Sheets-Shree?. l

FIG S July 24, 1951 l.. Lr-:EcH

VARIABLE-OUTPUT HYDRAULIC PUMP Filed Feb. 19, 1948 3 Sheets-Shee't nOE 2f.

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VARIABLE-OUTPUT HYDRAULIC PUMP Filed Feb, 19, 1948 5 sheets-sheet 's o "I e e9' V9-V 54 s6 u l l @CL 52 5o 33 64 INVENToR. AWQE/VKE 55C/4 Patented July 24, 1951 Lawrence Leech, Ryde, England Application February 19, 1948, Serial No. 9,348 In Great Britain November 27, 1946 Section 1, Public Law 690, August 8, 1946 Patent `expires November 27, 1966 Claims. (Cl. 103-37) v,This invention relates to a variable-output hydraulic pump of the kind having a rotor with a circle of axially-extending cylinder bores there# in, and plungers carried in the bores co-operating withva cam ring so as to be successively reciprocatedon rotation oi' the rotor, the cam ring being adjustable to vary the output.

My main object is to provide a pump of this kind which is pressure-balanced in a very satis factory manner and of which the control. can be very conveniently eiiected.

According to the invention, each of the cylinder bores, in the rotor, has a pair of plungers therein biassed away from one another respectively to Contact multiple-cam rings. There is a `stationary valve spindle having multiple ports which are in communication with inlet and delivery passages and which successively coact, on rotation of the rotor, with ports in the rotor leading to each of the bores between the pair of plungers therein. In addition, means is provided for twisting one cam ring, about the rotor axis, relatively to the other to vary the phase of reciprocation of each pair of plungers and therefore to vary the pump output.

Preferably each cam ring has a pair of diametricallyMopposite high points, and, between them, diametrically-opposite low points, and there are preferably two diametrically-opposite inlet ports (in the valve spindle) and, between fr them, diametrically-opposite delivery ports, the roto;1 having an even number` of symmetricallyarranged bores-for example, eight.

The adjustment of the one cam ring, in a direction to reduce the pump output, may be effected automatically, in conditions of excess pressure, `by aspringreturned plunger (referred to hereinafter as the rack `33) to which the delivery pressure is applied.

alternatively, the delivery pressure may be applied to aspiring-returned plunger (referred to hereinafter by the numeral 5l) operating a valve by which, in conditions of excess pressure, the deliveryV pressure is applied to a plunger (rack 33) by which the one cam ring is adjusted in the direction to reduce the pump output. In this case an adjustable abutment `may be provided, for control purposes, lfor limiting the return movement of the last-mentioned plunger towards the maximum delivery position.

In the accompanying drawings:

Figure l is a sectional end elevation of a pump 1 according to vthe invention, the section being taken 4 mainly on thellne I-I of Figure VH2, with the upper portion of the hydraulic control shown out of position, i. e., at the top;

Figure 2 is a longitudinal half-section thereof;

Figure 3` is a section or the upper part or the hydraulic control shown in Figure l but taken on a plane at right angles to that of Figure l and with the plunger 5l omitted;

Figure 4 is a fragmentary plan of the stationary valve spindle showing one of the inlet passages;

Figure 5 is a cross-section, taken on the lines 5-5 of Figures 2 and 4, through the stationary valve spindle; i

Figure 6 is a developed view of the adjustable multiple cam;

Figure 7 is a fragmentary view, of the lefthand upper port of Figure 1, showing the parts in the positions they `occupy in conditions of excess pressure; and

Figures 8 to 10 are sections taken, respectively,A

on the lines {L -8, 9-9 and Ill-I0 of Figure 7.

The drawings show a stationary casing 'built up of an end Wall I2, a cylindrical portion I3 and an end wall I4 which are secured to one another,

as by means of studs and nuts I5. In the end wall I2 is journalled, as by means of a ball bearing IS, a driving shaft IT which is keyed at I8 to a rotor I9 in the interior of the cylindrical por--` tion I 3. The rotor has in it eight axially-extending bores, of which one (20) appears in Figure 2, and in each bore is a pair of plungers 2|, 2| iassed apart from one another by means of a compression spring 22T. At the outer end of each plunger is secured a bearing pad 23, 23, The one lot of bearing pads coact with a lixed cam ring 2li and the other lot with an angularly adjustable cam ring 25. Each of the cam rings has an operative surface, as shown by Figure 6, giving two high points 2l', 21a and two low points 28, 28a, so that the associated plungers will be completely reciprocated twice during each revolution of the rotor.

The adjustable cam ring 25 is carriedby a sleeve 29 journalled in the end wall I4 by means of a thrust bearing 3l), and it is formed peripherally with rack teeth, indicated at 3|, extending over an angular distance which `is greater than The rack teeth are engaged with teeth 32 of an axially-slidable rack 33. the rack 33 the output of the pu-mp can be varied by varying the phase of reciprocation of the I plungers of each pair of plungers.

The rotor I9 has a central bore receiving a co axial stationary valve spindle 35 which extends through the end wall I4. The rotor also has .in

By operation of it eight radially-extending ports, of which one is shown in Figure 2 at 33, which respectively communicate with the eight longitudinal bores 2l) therein. The inner ends of the ports 3B coact -with'ports in the valve spindle 35. rlhe latter has two diametrically-opposite ports 31 which are at all times incornmunication with an4 outlet or delivery passage 33 provided along the centre of l the valve spindle 35. The latter also has a waisted portion 33 enclosed by a sleevell providing an annular passage GI which is 'the inlet or supply passage, being fed, by means not shown, from an annular passage 42 throughopenings of which one is shown at 43. v l. 4

The axially-inner end of the valve spindle has, communicating with the annular space 4I,4

two passages 45 (Figure 4) terminating with inlet ports 46 (Figures 4 and 5) which are diaposition shown of the rod 48 the rack is in a position in which the adjustable cam ring25 is in phase with the cam ring 24 (i. e., both rings have their high spots aligned, so that both plungers of each pair move inwardly in synchronism), the pump thus giving its designed maximum delivery. By moving the rod 48 to the right the abutment position of the rack 33 will be correspondingly adjusted to cut down the maximum delivery of the pump below the designed value, when the plungers of each pair are reciprocating out of phase to an extent vdependent upon the setting of the control rod.

- The rack 33 is shown in this instance in the form `of `a hydraulic plunger, the space 50 at its operative end communicating with a passage 5| in a body 52. This body 52 has in it a bore 53 communicating with a drain 55 (Figure 3) connected, for example, to the supply tank, and with the parts in the position shown in Figure 1 the passage 5| is in communication with the drain 55 by way oia waisted portion 56 of a plunger 51 slidingly mounted in the bore 53. The latter also communicates with a passage 63 externally connected by a pipe 12 to a passage 3| (Figure 2) connected to the delivery passage 38. The passage 68 is also connected by a passage S2 to the adjacent end of a hydraulic cylinder 83 having therein aplunger head 64 pressed to the position shown by means of a spring 85 adjustably supported by a hollow nut 33, the' plunger head B4 being fast with the plunger 51.

Thus the delivery pressure is at all times applied tothe plunger head 64 by way of the passage Gl, the pipe 12, and the passages G3 and 62.

The nut 6E is set tomaintain the plunger 51 in the position shown in Figure 1 whilst ordinary delivery pressures obtain; but when the said pressure exceeds a predetermined value the plunger 51 is moved to the right (Figure l),

thereby disconnecting the passage 5l from the drain 55, and in due course aligning it with a port 68 connected to a bore 63 in the plunger 51, as shown by Figures 1 and l0. The plunger 51 has another port 1U, in connection with the bore 63. which` when the port B8 is aligned with the passage 5l is itself aligned with the passage 60. The delivery pressure is then passed from the passage through 'the port 10, along the bore 89, through the port 68, and along the bore 5| to the operative space 50 to force the rack 33 to the'ri'ght, asv shown by Figure .7, this twisting the cam 25 in a; direction to reduce the pump output. When the excess pressure is released by this means the spring returns the. plunger 51 to the position shown, thereby again placing the operative space 50 in connection with the drain 55, as shown by Figure l, and allowing the rack 33 and the cam 25 to return to the position of maximum delivery dependent upon the setting of the control rod 48, the cam 25 being biassed to turn in this way by frictional engagement with the rotating pads 23. At the same time the bore 69 in the plunger 51 is placed in communication with the drain 55 byv way of a port 54 in the plunger.

If adjustment of the pump (by meansof'the rod 48) is not required the delivery pressure maybe taken directly to the operative space 50, and a spring applied to the rack 33 to balance the delivery pressure until it reaches a predetermined value, as will be well understood, when excess pressure will actuate the rack.-

What I claim as my invention and desire to secure by Letters Patent of the United States is:

l. A variable-output hydraulic pump including a stationary casing, a rotor having a circle of axially-extending bores therein, a pair of plungers in each bore, a multicam ring at each end of the` rotor, spring means biassing each pair of plungers apart and into contact with the adjacent cam ring, a stationary spindle extending into a coaxial bore of the rotor from one end, said spindle having in it multiple ports which arein communication with inlet and delivery passages and which successively coact, on the rotation ofthe rotor, with ports in the rotor leading to each of the bores between the pair of plungers therein, a driving shaft extending into the coaxial bore of the rotorl from the other end and having a driving connection with therotor, said drivingy shaft journalled in said stationary casing, and means for twisting one cam ring about the rotor axis relatively l to the other cam ring to vary the phase reciprocation of each pair of plungers and therefore the pump output.

2. A pump, according to claim l, characterised in that each cam ring has a pair of diametricallyopposite high points and, between them, a pair of diametrically-opposite low points, and in that there are two diametrically-opposite inlet ports in said spindle and, between them, diametricallyopposite delivery ports, the rotor having an even number of symmetrically-arranged bores.

3. A pump, according to claim 1, characterised in that said means for twisting said one cam ring includes an operating plunger to which the delivery pressure is applied.

4. A pump, according to claim 1, characterised in that said means for twisting said one cam ring includes an operating plunger, a valveby which the delivery pressure is applied to said operating plunger, and a spring-returned plunger to which the delivery pressure isapplied and which conl trols said valve.

` 5. A pump, according to claim 1, characterised in that said means for twisting said one cam ring includes an operating plunger, a valve by which the delivery pressure is applied to said operating delivery pressure is applied and which controls said valve, and en adjustable abutment for limiting the return movement towards the maximum delivery position o1' said operating plunger.

LAWRENCE LEECH.

REFERENCES CITED The following references are of record in the ille o! this patent:

Number l0 Number a y UNITED STATES PATENTS Name Date Robertson Apr. 18, 1916 De Leeuw May 15, 1928 Robinson Mar. 4, 1941 Higgins Nov. 2, 1943 Mercer Apr. 13, 1948 FOREIGN PATENTS Country Date Great Britain 1914 

